1. Field of the Invention
The present invention relates to a facsimile machine which has a function of storing image data and is adapted for communications based on a plurality of communication modes and, more particularly, to an improvement in a method for controlling an interval and frequency of a re-call necessary due to the busy state of a party according to the communication modes and communication quantities.
2. Description of the Related Art
For example, when a facsimile machine is connected only to a telephone line or a DDX line, the re-call frequency and interval of the facsimile machine are set at desired preset values so that, when a called party is busy, re-call is tried by the preset number of times within the preset interval.
In this case, since a plurality of terminals connected to the above line have similar operating characteristics (for example, communication rate), effective re-call control can be achieved, from the viewpoint of a line operating efficiency, by setting the re-call interval and re-call frequency at the preset fixed values as mentioned above.
Recently, a new integrated services digital network (which will be referred to as the ISDN, hereinafter) has been created. ISDN is heterogeneous to the aforementioned existing line network and synthetically handles different communication services.
A facsimile machine adapted for the ISDN not only can perform G4 communication on the ISDN line but also can form a single communication network, for example, by interworking with the existing telephone line network to also realize G3 communication with a facsimile machine of a G3 communication type in the existing telephone line network.
In other words, the ISDN facsimile machine has a function of handling a plurality of different communication modes including G3 and G4 communication through the ISDN.
Accordingly, with the facsimile machine having a function of handling a plurality of different communication modes, when the re-call frequency and re-call interval are set to a fixed value as mentioned above, the facsimile machine's line operating efficiency is reduced due to a difference in communication rate between the G4 and G3 communication (usually, 64 Kbps for the G4 communication and 9.6 Kbps for the G3 communication).
For example, when the re-call interval for the busy party is set based on the G4 communication, the re-call interval becomes so short in the G3 communication that the re-call often results again in the busy party. However, when the re-call interval for the busy party is set based on the G3 communication, the re-call interval becomes too long in the G4 communication and requires a long time to terminate the transmission.
Generally speaking, a communication quantity (a communication frequency and a traffic quantity) tends to vary greatly from day-to-day or time-to-time. For example, when the re-call interval is set based on less traffic quantity, such a situation that the party is busy often occurs at the time when traffic quantity is great. However, when the re-call interval is set based on more traffic, a time necessary for transmission completion becomes remarkably long.
In this way, the prior art facsimile machine adapted for a plurality of different communication modes has had the problem that, with regard to re-call control required due to a busy party, since the re-call frequency and re-call interval are set to have a fixed value, the re-call interval becomes so short in certain communication modes, and communication quantity results again in encountering the busy state. Alternatively, the re-call interval becomes too long in certain communication modes, and communication quantity results in requiring a long time to access the party, whereby its line operating efficiency is eventually reduced to a large extent.